Buchla 200e series, Руководство пользователя

Страница: 61 / 78

Model 260e Barber Pole Module
26005010
Now just what is a "barber pole" module? A barber pole, used in a bygone era
to identify haircutting saloons, is a spiral (resembles a candy cane) that slowly
turns around a vertical axis. The actual movement is rotational and horizontal;
the perceived movement is vertical, but illusory. The term has been applied to
processes in which movement is perceived to occur continuously in one
direction, but ultimately there is no net movement (in that direction). The
barber pole stems from another service offered by barbers – that of using
leeches to suck blood from clients. The blood-soaked rags were laid out in he
sun to dry, and the pole is an abstract reminder of the resultant bloody mess.
The term "barber pole" refers to an auditory illusion that can be readily
produced by this module. Called the Shepard tone paradox (after its inventor,
Roger Shepard), one's perception is that each note in a forever ongoing series
of notes is higher in pitch than the preceding note. The illusion works in
reverse also, with each note perceived to be pitched lower than its
predecessor. M. C. Escher's "Ascending and Descending" is occasionally
cited as a visual equivalent of the auditory paradox.
Model 260e Duophonic Pitch Class Generator
Two independent, voltage controlled pitch class generators. (A pitch class
generator produces a singular pitch in every perceivable octave.) Frequency
modulation inputs and a five band spectrum-shaping facility are provided.
When switched to the "barber pole" mode, an internal computer takes over
pitch control of both generators, and issues pulses for triggering an external
envelope generator (like a model 281e function generator), which in turn can
drive a voltage controlled amplifier (like a model 292e dynamics manager).
When the 260e's output signals are gated through the latter, Sheppard tones
and other auditory illusions (such as the tri-tone paradox) may be produced.
In this mode, only the left f.m. input is active, affecting both oscillator sections.
When switched to the “continuous” mode, the right oscillator descends while
the left ascends (or visa versa). The rate of change is variable to 2.5 octaves
per second in either direction, and is voltage controllable. Additionally, the
pitch intervals can be adjusted from quarter-tones to tri-tones.
With its multi-voicing, equalization, and frequency modulation capabilities,
you will find the 260e musically more interesting than the standard Shepard
tone generator used in perceptual psychology experiments.
Settings of all pots and switches can be locally stored and subsequently
recalled by the model 225e or 206e preset manager.
To connect or disconnect this module from the central library function, push
the remote switch. A lighted red LED signifies a connection.